This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Clinical breast exams have limited specificity and sensitivity for detecting breast tumors. Even X-ray mammography, which is used for early screening of breast tumors, has limited sensitivity and does not detect approximately25% of breast cancers. Dynamic contrast-enhanced MRI (DCE-MRI) has high sensitivity but low specificity;i.e., both cancerous and benign lesions enhance [2]. Additional imaging modalities such as sodium (23Na) MR have the potential to increase the sensitivity and specificity of breast cancer detection because 23Na MR can reflect the disruption of the membrane Na-K pump associated with cancer. Moreover, recent advances in gradient hardware and pulse sequences have made 23Na MR feasible for quantitative measurements of sodium concentration. Preliminary results of multinuclear MRI using a receive-only H surface coil and a transmit/ receive 23Na surface coil show elevated 23Na signal in the tumor. Although the surface coil provides high SNR images, there is significant B1 inhomogeneity as modeled by Biot-Savart's law. For quantifying 23Na concentration in the breast, we need an RF coil that improves B1 homogeneity without sacrificing SNR. The goals of this study were to build a dual-tuned Helmholtz coil, to investigate the difference between a dual-tuned Helmholtz coil and a dual-tuned surface coil in providing high SNR and high quality B1 homogeneity for multinuclear imaging, and to perform preliminary breast imaging using the dual-tuned Helmholtz coil.